It is generally fast except between 10am-12pm every day (i.e. when the tatkal systems open) and that is what frustrates most people. When called out on these issues, IRCTC has consistently refused to add capacity to deal with the demand between 10am-12pm. You are correct that this could be solved by using quotas and reservations but they haven't done that. My only guess is that it is for political/bureaucratic reasons. It's easier to blame capacity issues than tell the reality.

>reserved a certain proportion of the tickets for rural users

This already happens. There are quotas of different kinds.

P.S. You know what? You are actually right. There's no technical reason for this to be the way it is. They are using that explanation as a cover for a political or legal problem or by occam's razor, they probably have a fixed budget (and not allowed to use on-demand services like AWS) and the govt won't approve the budget necessary to solve the capacity issues between 10am-12pm.

Second, fake IDs are easy to make.

Third, it's impractical to enforce on the ground. Indian Railways is relatively open access compared to airlines. On average, trains begin boarding 15-30 mins prior to departure and have a very high number of passengers. With an avg of 16 coaches per rake, with each coach having 60-100 passengers, each train is carrying 960-1600 passengers. Some trains are even longer and most trains are over capacity because 2nd sitting has no reservation and people just pile on as far as there is room in the coach. It's pretty impractical to verify tickets of 1000+ people along with their ids. If you are departing out of a major city, its usual for TTEs to verify tickets after 2-3 hours (and after smaller stations have been crossed.)

Tickets have been hogged and scalped for a long time in India. I'm the first in my family who has no concept of bribing or buying scalped tickets or engaging an "agent." Everyone of the previous generation has plenty of stories about their experiences before. There is still a long way to go to improve access but I will also not deny that there has been a significant improvement compared to my parents experience.